The invention relates to a device for interconnecting structural parts by means of a connecting screw. A distance holder is arranged between the structural parts to be connected and is traversed by the connecting screw, which holder is adjustable lengthwise in response to the screwing-in movement of the connecting screw in order to become pressed against one of the structural parts.
In EPO Document No. 176 663-B1, a device of this type is described in which the distance holder comprises a distance washer which presses tightly against the outer thread of the connecting screw so as to be in frictional engagement therewith. This distance washer supports itself with its outer wide side on the one structural part and with thread pitch surfaces on the counter pitch surfaces which belong to the other structural part. If the distance washer is turned during the screwing-in of the connecting screw, the axial position of the distance washer is thus changed. In a suitable screwing direction of the thread pitch surfaces, the distance washer moves in the axially opposite direction to the screwing-in direction of the connecting screw, so that the one structural part can be braced between the distance washer and the head of the connecting screw. In this device, the distance holder is formed directly by the distance washer and the corresponding counter-pitch surfaces. Thereby a construction is achieved that is technically simple to manufacture. There is one disadvantage in that, during the bracing, the distance washer turns relative to the braced structural part which it engages, so that scratch marks or lacquer damage on this structural part can result and thus increasing the corrosion danger.
It is the object of the invention to create a device of the initially mentioned type in which damage of the structural parts can be avoided through a distance holder.
The problem is solved, according to the invention, in that the distance holder has two supporting bodies which are held non-rotatably on one of the structural parts, can be slid axially against one another, support themselves each on one of the structural parts, at least, one of the supporting bodies forming a screw drive together with the control element.
This solution has the advantage that the distance holder supports itself with two torsionally strongly held supporting bodies on both of the structural parts, so that, at the supporting surfaces, no relative turning occurs which could lead to damage or an increased rub resistance.
In a preferred embodiment, the control element cooperates with the supporting bodies to form two screw drives which differ in their threading pitch and/or their screwing direction. If the screwing direction of the screw drives runs opposite, then, with a given threading pitch and angle of rotation of the control element, a doubling of the lift is achieved. If the screwing direction is the same but the threading pitch differs, the change of the axial size of the distance washer is proportional to the difference between both threading pitches, so that a very sensitive adjustment of the distance is made possible.
The threads of the screw drives can be arranged as inner and outer threads at the peripheral surfaces of the supporting bodies and of the control element. They can, however, also be arranged as screwing surfaces at the frontal sides of the supporting bodies and of the control element.
Both of the supporting bodies are preferably locked together, such that they are held together permanently. Furthermore, it is useful to dispose at least one of the supporting bodies in a plastic housing which, at the smallest possible axial length of the distance washer encompasses both supporting bodies and also the control element. This reduces the danger of an unintentional adjustment of the control element and thus facilitates the automatic feeding of the device in automated installation processes.